On 12/5/08 8:55 PM, "WarrenS" <[EMAIL PROTECTED]> wrote:
>
>
> To Björn
> wow, neat, mm accurate antennas,
> That means the RF way still has some hope.
> How does it get the information down the cable without unacceptable loss of
> accuracy?
> Anyone know how they make these antennas, and can it be done with small cheapy
> ones?
>
Nothing really special. Mostly, it's care in the surroundings.. A series of
choke rings to suppress multipath reflections from under the antenna.
Actually, putting the usual inexpensive hockey puck style antenna on a
cookie sheet makes a fair approximation.
The other thing is that they get calibrated. You make a series of
observations of the signals from GPS satellites as they move overhead. You
know where the satellite is, and where the antenna is (in a long term
averaging sense), and you can calculate the phase center position as a
function of look angle.
I think the GIPSY software does this for you.
Once you know what a particular design does, then it's more a matter of
construction tolerances.
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